Method of preparing an alkaline concentrate of mahogany sulfonates



Patented May 1 1, 1954 CON CENTRATE OF FONATES MAHOGANY SUL- Lionel 'S. Galstaun, Oakland, Calif., assignor to Tide Water Associated Oil Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application June 8, 1951, Serial No. 230,681

-5 Claims. (01. 25233) kalinity. It is a further object to utilize such sulfonates in lubricating oil compositions of value in the lubrication of diesel engines operating on high sulfur fuels. Other objects may be apparent from the following description.

Among the many additives which have been proposed for oils designedfor use in the crankcases of internal combustion engines, one of the most common types employed is the metallic salts of sulfonic acids, generally referred to as metal sulfonates. Of these, the salts of mahogany sulfonic acids derived from the sulfonation of petroleum oils have found wide usage, alone or in combination with other additives, as detergents in crankcase oils. Recently, with the more extended use of diesel fuels having a high sulfur content, the art has shown a preference for mahogany sulfonates which have an alkaline reaction, as these, in addition to their detergent properties, have proved helpful in counteracting the efiects of acidic combustion products which find their way into the crankcase when high sulfur fuels are used. In fact, it appears desirable for the sulfonate to have as high an alkalinity as possible.

A method which has been proposed for producing alkaline mahogany sulfonates is to subject a selected petroleum oil fraction to sulfonation with concentrated or fuming acid, whereby mahogany sulfonic acids are formed dissolved in the oil. After separation of the acid sludge, the dissolved sulfonic acids are neutralized by the addition of an excess of lime or other oxide or hydroxide of an alkaline-earth metal thereby forming alkaline earth mahogany sulfonate dissolved in the oil. In order to prepare a concentrate of the sulfonate forblending into other oils, the sulfonate-containing oil is subjected to distillation with steam or vacuum in order to remove the major part of the oil. By this procedure it has been possible to produce a sulfonate concentrate having an alkalinity indicating an excess of alkaline earth metal over thattheoretically required to produce a neutral sulfonate. Though not exactly known, it is thought that the excess alkalinity is caused by the presence of basic sulfonates in the product.

According to the present invention, I have found that, by conducting the distillation step under very high vacuum and with extremely short heating period, in the order of one minute or less, sulfonate concentrates can be prepared having an alkalinity practically double that produced with conventional vacuum or steam distillation, with corresponding increase in effectiveness when blended in diesel lube oils. I have also found that, by proper selection of stocks for the sulfonation step, the alkalinity of the final concentrate may be further increased.

While in its broader aspects the invention may be practiced by sulfonating almost any sulfonatable petroleum fraction, the preferred oil for the sulfonation step is a Mid-Continent oil fraction which has been previously refined by the well known furfural selective solvent extraction process and which has a viscosity of about 150 to 400 seconds S. U. 100 F. I have found that this type of stock produces greater yields of sulfonates of lower viscosity thereby permitting greater concentration without producing an unmanageable concentrate. Pretreatment of the stock by other selective solvent processes, or even by 98% H2SO4, may be found to be equivalent in some respects to the furfural refining. The base oil is sulfonated by contact with a sulfonating agent such as sulfuric acid of 9 8% to 108% strength. However, I prefer to use 103% fuming acid, and to apply the acid in three successive treatments of 30 pounds per barrel each, removing the acid sludge formed at each stage before the succeeding stage. A temperature range of to 150 F. have been found satisfactory for each stage but F. to F. is preferred. The three stage treatment is to be preferred over a single stage of 90 pounds per barrel, as it is found to produce a greater yield of sulfonic acid. After three stages of 30 pounds per barrel each vary little, if any, further sulfonation will occur by further treatment with additional acid. The acid sludge from the last stage is completely removed by centrifuging, filtration, or other equivalent procedure.

To the acid-oil there is added lime, barium hydroxide, or other alkaline earth oxide or hydroxide in an amount at least double that theoretically required to neutralize the acidity of the oil. It has been found convenient to add the base in the form of a paste containing about 2% free water. The mixture of oil and base is thoroughly agitated until the reaction is complete, which may take an hour or so. The reaction may be assisted, especially toward the end, by heating to a temperature not exceeding about 300 F., using pressure, if desired, to avoid volatilization of the water. After neutralization the oil is clarified by filtration, using a filter-aid if desired, to yield a solution of alkaline earth metal sulfonate in a very highly treated 011 stock. I

The sulfonate content of the oil may be about more or less, depending upon various factors such as the stocks chosen for sulfonation and the sulfonating conditions.

Though this oil-sulfonate solutionmay have some commercial utility, eitheras a lubricant per se or diluted with other oil, the oil constituent thereof is not well suited for diesel engine lubrication due, among other things, to the fact that the oil has been too highly treated with acid and the probability that the viscosity is different from that desired. Accordingly, the oil-solution is distilled to remove the greater portion of its oil content. For the purposes of the invention such distillation is carried out in a still capable of conducting the distillation at temperatures below about 300 F. while maintaining the oil at such temperature for a maximum of one minute.

A type of still suitable for conducting such dis tillation is that type generally referred to as molecular stills by those familiar with high vacuum, short path, short heating cycle distillation. In one form of these stills oil is fed upon a heated rotating plate within an assembly which is held at a high vacuum in the order of 2 to microns of mercury. During the extremely short time that the oil is in contact with the plate, vaporization occurs and the vaporized'rnolecules impact a cooled surface adjacent to the rotating plate, the distance between the two being in the order of the meanefree path of the vaporized molecules. Another form of these stills adaptable for carrying out the invention is described in U. S. Patent Number 2,210,928 issued August 13, 194.0, to K. C. D. Hickman.

From the distillation of the sulfonate-oil solu tion a distillate oil is recovered. amounting in volume to about to of the charge to the still. This distillate oil is normally a light colored oil suitable for use as a technical white oil and may be disposed of as desired. The residue from the distillation isv the desired concentrate containing roughly 50% by weight of alkaline-earth sulfonate having an alkalinity remarkably higher than that produced by conventional distillation of similarly produced sulfonate-oil solutions. The concentrate may be added in any desired amount to suitable oils for the preparation of diesel lubricants. Due to the high alkalinity of the sulfonate, diesel lubricating oils prepared with the concentrate exhibit a great efiectiveness in nullifying the detrimental effects which sulfur containing fuels have on the lubricating oil.

The following examples illustrate the great improvement resulting from low temperature, practically instantaneous distillation compared with conventional distillation.

EXANIPLEI I Ten gallons of neutral OiLmanufactured-by iurfural solvent extraction, solvent dewaxing,

final clay treatment, and having the properties shown in'Iable I, weresulionated at F.

.bined Water.

with a total of 90 pounds of 103% fuming sulfuric acid per barrel of the oil.

Table I Gravity, API 30.1 Flash, 01. O. 0. F 435 Viscosity, second S. U. 100 F 210 Viscosity index Color, ASTM 2+ The fuming acid was applied in three treatments of 30 #/bbl. each, and sludge separated from the oil at each stage. After the sludge from the last stage wasseparated, the acid oil was centrifugedto remove the last traces of sludge.

The acidoil was then titrated to determine its acidity and neutralized at room temperature, using double the indicated number of equivalents of barium hydroxide. The hydroxide was added to the acid oil in the form of a paste of the octasulfonate stock was filtered in a filter press.

Yield at this stage was 6.5 gallons of sulfonate stock comprisingsulionate dissolved in highly treated oil.

A portion of the filtered sulfonate stock was then charged to a molecular still operated at an absolute pressure of 12 microns of mercury at a temperature of 290 F. The overhead distillate amounted to 80.3%, and the residue 19.7%, by volume of the charge to the still. The properties of the residue, or concentrate, are shown in Table II.

EXAMPLE II A second portion of the filtered sulfonate stool: was charged to steam still and distilled until 75% of the still. charge wasrecovered as distillate. Further concentration in the steam still was impractical because the steam distillation was terminated when the temperature of the oil reached 650 F. A concentrate amounting to 25% by volume of the still charge Wasrecovered and its properties are compared in Table II. with those of the concentrate derived from Example I.

Table II ggg g Residue Residue Before from Exfrom Fro Dist ample I ample 11 Yield, percent 19. 7 Gravity, API 23. 3 3. 8 8.1 Viscosity, SSU 100 F 232 1698 1290 Viscosity, SS U 210 F". 49. 3 131. 7 113 Ash (as sulfate) percent 5. 8 19.3 15.3

Cale. Sull'onatc Content Approx,

percent 10 50 40 Alkalinity (as mg. K011 per gm.) 9. 62 27. 7 13. 62

It will be noted from Table II that the concentrate prepared in Example I possessed-a remarkably higher alkalinity than that of Example II even after allowance is made for the increased concentration which was obtainable in Example I.

EXAMPLE III The processin steps of Example I were repeated using, for the oil to be sulfonated, a furfural solvent refined, solvent dewaxed and clay finished East Texas oil of the following properties:

Gravity, API 29.1 Viscosity, SSU 100 F 450 Viscosity, index 94 Color, ASTM 1% Pour point F 20/25 The results obtained are shown in Table III.

Table III Residue xamp e fore Dlst. In

Yield, percent 100 17. 4 Gravity, API 23. 5 4. 2 Viscosity, SSU 100 F 516 4572 Viscosity, SSU 210 F 66. 4 261 Ash (as sulfate) percent 4. 94 18. 5 Cale. Sulfonate Content Approx, rcent. 8. 5 50 Alkalinity (as mg. KOH per gm.) 8. 64 30. 4

In the examples above barium hydroxide was used to neutralize the sulfonic acids. Calcium and strontium hydroxides may also be used. With the use of calcium hydroxide, it is occasionally found that the calcium sulfonate concentrate is very viscous and, consequently, difl'icult; to handle. In such cases the use of one equivalent of calcium hydroxide followed by an equivalent of barium hydroxide will generally result in sulfonate concentrates having desired high alkalinity and relatively low viscosity. Thus, in a specific embodiment, the invention contemplates the use of two or more alkaline earth metal hydroxides in combination.

Concentrates prepared as described above may be blended in various percentages in petroleum lubricating oils of suitable grade for diesel lubrication. The higher alkalinity resulting from distillation in stills of the molecular type permits the use of less concentrate to provide the same protection against high sulfur fuels, or, with the same percent of added sulfonate, substantially greater protection against the high sulfur fuels is obtained. Ordinarily, percentages of the concentrate ranging from about 1% to about 6%, iving a sulfated ash content to the finished oil of about 0.2% to about 1.2%, have been found most useful though, in its broadest aspects, the invention i not limited by the specific values. In fact, under extremely severe diesel service, even larger amounts, such as 10% of concentrate, or even higher are of practical advantage. As is obvious, other additives may be added to the oil for other purposes, such as for example, corrosion and oxidation inhibitors, pour point depressors, and the like. Likewise, the concentrates of this invention may be used in combination with other detergents. As an example, the highly alkaline concentrate of the invention has been found to b very satisfactory for use in conjunction with calcium phenate, especially in the proportion of about 2 parts concentrate to about 2 to 3 parts calcium phenate.

As an example of a finished diesel lubricating oil prepared according to the invention, to a solvent refined Mid-Continent oil having a viscosity of 65 S. S. U. 210 F. and a viscosity index of 95 there is added a concentrate similar to that described in Example I and also an oxidation or bearing corrosion inhibitor comprising zinc alkyl thiophosphate in the following proportions:

Since the concentrate, inhibitor and oil are all liquid the blending is readily done by simple mixing, using some heat to reduce the viscosity of the components and/or mixture. The resulting oil, containing about 3% sulfonate of high alkalinity, although substantial improvement can be found even at 1% sulfonate, is well suited for the lubrication of diesel engines, especially those operating on high sulfur fuels, although it is also of utility in other applications, such as gasoline fueled engines where conditions are normally unfavorable to oil stability.

I claim:

1. The method of preparing an alkaline concentrat of mahogany sulfonates useful as diesel lubricating oil component, which comprises: sulfonating a petroleum oil with a sulfonating agent to produce mahogany sulfonic acids dissolved in oil, removing the spent sulfonating agent, treating the oil containin sulfonic acids with an alkaline earth metal base in amount at least double that required theoretically to neutralize said acids thereby converting said acids to alkaline earth metal sulfonates dissolved in the oil, and distilling the thus neutralized oil at a temperature of not over about 300 R, at a pressure not exceeding 50 microns of mercury and with a heating cycle of not over one minute to remove the major part of the oil content as distillate and leave as residue an alkaline reacting concentrate of sulfonates dissolved in oil.

2. The method of claim 1 in which the petroleum oil is a refined Mid-Continent oil fraction having a Saybolt Universal viscosity at F. between and 400 seconds.

3. The method of claim 1 in which the alkaline earth metal base is a member of the group consisting of calcium oxide, calcium hydroxide, and barium hydroxide.

4. The method of claim 1 in which the oil containing sulfonic acids is treated with approximately one equivalent of calcium hydroxide and then with at least one equivalent of barium hydroxide thereby converting said acids to relatively low viscosity sulfonates dissolved in the oil.

5. In the concentration of alkaline reacting alkaline earth metal mahogany sulfonates dissolved in a viscous oil, the improvement which comprises distilling ofi excess oil from the sulfonate-oil solution at a temperature below about 300 F., at a pressure below 50 microns of mercury, and with a heating cycle not exceeding about 1 minute, whereby the sulfonate concentrates thus produced have a greatly increased alkalinity over that which would be obtained by conventional vacuum or steam distillation.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,229,209 Houghton Jan. 21, 1941 2,402,325 Griesinger June 18, 1946 2,467,176 Zimmer et a1. Apr. 12, 1949 2,485,861 Campbell Oct. 25, 1949 2,501,731 Mertes Mar. 28, 1950 2,617,049 Asseif Nov. 4, 1952 

1. THE METHOD OF PREPARING AN ALKALINE CONCENTRATE OF MAHOGANY SULFONATES USEFUL AS DIESEL LUBRICATING OIL COMPONENT, WHICH COMPRISES: SULFONATING A PETROLEUM OIL WITH A SULFONATING AGENT TO PRODUCE MAHOGANY SULFONIC ACID DISSOLVED IN OIL, REMOVING THE SPENT SULFONATING AGENT, TREATING THE OIL CONTAINING SULFONIC ACIDS WITH AN ALKALINE EARTH METAL BASE IN AMOUNT AT LEAST DOUBLE THAT REQUIRED THEORETICALLY TO NEUTRALIZE SAID ACIDS THEREBY CONVERTING SAID ACIDS TO ALKALINE EARTH METAL SULFONATES DISSOLVED IN THE OIL, AND DISTILLING THE THUS NEUTRALIZED OIL AT A TEMPERATURE OF NOT OVER ABOUT 300* F., AT A PRESSURE NOT EXCEEDING 50 MICRONS OF MERCURY AND WITH A HEATING CYCLE OF NOT OVER THE MINUTE TO REMOVE THE MAJOR PART OF THE OIL CONTENT AS DISTILLATE AND LEAVE AS RESIDUE AN ALKALINE REACTING CONCENTRATE OF SULFONATES DISSOLVED IN OIL. 